Electrocatalysis of hydrogen evolution by synthetic diiron units using weak acids as the proton source: Pathways of doubtful relevance to enzymic catalysis by the diiron subsite of [FeFe] hydrogenase

摘要: Abstract IR spectroelectrochemical studies of bis(thiolate) and dithiolate-bridged diiron carbonyl compounds, [Fe 2 (μ-SR) (CO) 6 ], show that the primary reduction process results in rapid chemical reaction, leading to two-electron reduced products. When reaction is conducted under an inert atmosphere, major product (μ-SR)(μ-CO)(CO) ] 1− , where case neutral compounds has one bridging non-bound sulfur atom. This formed near-quantitative yield for solutions saturated with CO. Reduction occurs at potentials near −2.0 V vs. SCE give a range products including [Fe(CO) 4 2− . thiolate-bridged mild presence CH 3 COOH leads formation this accompanied by acid-base dissociated thiolate. The largely reversible recovery ca. 90% starting compound COOH. In acid, proceeds without generation observable concentrations structurally related one-electron compound. Electrocatalytic proton achieved when potential stepped sufficiently negative reduce observation keeping cyclic voltammetry system. Since catalytic species involved weak-acid reactions distinct from material, subsite hydrogenase H-cluster, these experiments are dubious relevance biological